Conventional mouthwash compositions frequently contain ethanol, up to 27% volume, as a preservative and antimicrobial agent. In some individuals, alcohol may exacerbate xerostomia (dry mouth), which in turn can cause halitosis and significant tooth decay, as the protective effect of saliva's remineralizing the enamel is reduced. Xerostomia also makes the mucosa and periodontal tissue of the mouth more vulnerable to infection and increases the risk of gingivitis. Mouthwash comprising high levels of alcohol also may be undesirable for use by alcoholics, children, and members of certain religious faiths, and some consumers may object to the burning sensation of relatively high alcohol compositions.
Cetylpyridinium chloride (CPC) is a cationic quaternary ammonium compound frequently used in addition to or in place of ethanol as an antiseptic and preservative in mouthwashes, toothpastes, lozenges, throat sprays, breath sprays, and nasal sprays. At effective concentrations, e.g. ca. 0.07%, CPC kills bacteria and other microorganisms and has been shown to be effective in preventing dental plaque and reducing gingivitis. It is believed to kill bacteria by binding to the negatively charged phosphates of the bacterial cell membrane. Formulating CPC presents challenges, however, because of its bitter taste and its incompatibility with many composition excipients. Ethanol can be helpful in such compositions as it acts as a solubilizer for many ingredients and is a flavor enhancer, but a noted above, there are disadvantages to oral care products comprising ethanol.
There is a need for ethanol-free liquid oral care compositions having an acceptable taste.